The present invention relates to a pump for sucking or injecting a liquid from or into a living tissue, and in particular, to a precision screw pump suitable for sucking or injecting a viscous tissue fluid while minimizing invasion into the human body.
Conventional methods for sucking a biological tissue fluid from or injecting a liquid into a living body transfer a liquid by applying a negative pressure to a pipe to suck the liquid or applying a positive pressure to the pipe to extrude the liquid.
A recent growing demand for treatment methods with less invasion requires reduction in the diameter of a pipe inserted into a living body. On the other hand, the pipe frictional resistance increases in proportion to the viscosity of a liquid while decreasing in proportion to the pipe diameter, and a driving force for transfer further decreases in proportion to the square of the decrease in pipe diameter. Thus, it is difficult to use a pipe of a small diameter to transfer a viscous liquid inherently having a large pipe frictional resistance (FIG. 1).
Thus, small-diameter pipes can inevitably be used only for liquids of a low viscosity, and large-diameter pipes must still be used to suck or inject viscous tissue fluids.
If, however, a large-diameter pipe is used, for example, to treat tympanitis, a large amount of eardrum is disadvantageously incised upon insertion of the suction pipe. Besides, the large diameter of the suction pipe limits sites from which viscous pus can be sucked.
Likewise, when a large pressure is required in injecting a liquid, for example, the cerebrospinal fluid, a thick pipe must pierce through the body in order to obtain a high pressure sufficient to press the liquid surface.
According to the prior art, the pipe frictional resistance increases relatively with a decrease in pipe diameter, whereby it has been very difficult to reduce the diameter of the pipe to the extent that invasion into the living body can be minimized while maintaining an effective amount of liquid transferred. In particular, since it has been almost impossible to suck or inject a viscous liquid, which requires a high pressure for suction or injection, using a pipe of a very small diameter, suction or injection of a viscous liquid with less invasion is very significant.
An object of the present invention is to provide a suction and injection pump that can transfer a sufficient amount of viscous liquid despite the use of a very thin suction and injection pipe in order to provide means for enabling a viscous liquid to be sucked or injected while minimizing invasion into the human body.
Having made research to achieve this object, the inventors have found that introduction of a screw pump structure enables a liquid to be transferred only by means of the rotation of a rotor without depending on a pressure for sucking or pressing the liquid, that a viscous liquid can be moved by increasing the number of rotations of the rotor, and that the pipe diameter can be reduced by twisting up a plurality of very thin filaments to obtain a rotor of a very small diameter that can be rotatably housed in a thin pipe.
The present invention was made based on the findings that the transfer capability improves consistently with a decrease in friction between an inner wall of a needle and a transferred liquid or between the rotor and the liquid and that the screw pump prevents the amount of liquid transferred from being affected by a large gap between an outer periphery of the rotor and the inner wall of the needle, as long as the liquid has a certain degree of high viscosity.
The present invention provides a pump capable of minimizing invasion into human bodies by housing a very thin rotor in a cylindrical needle and positively transferring a liquid based on the mechanical configuration of the rotor so as to effectively suck or inject a viscous liquid while using this configuration to reduce the pipe diameter.
More specifically, the present invention provides a precision screw pump for injecting or ejecting a liquid into or from a biological tissue, as described below.
(1) A needle-shaped precision screw pump of a very small diameter for injecting or ejecting a liquid into or from a biological tissue.
(2) A precision screw pump in an instrument for injecting or ejecting a liquid into or from a biological tissue, comprising a cylindrical thin needle having an introduction port at one end and a discharge port at the other end, and a cylinder connected to one end of the needle and having a larger diameter than the needle, wherein
said cylindrical needle is a screw pump comprising a rotor housed in said needle for rotation along an axial direction thereof and a driver housed in said cylinder and connected to one end of said rotor for rotating the rotor, wherein
said rotor is a rotor obtained by twisting up a plurality of filaments and is rotated in synchronism with the rotation of said driver to transfer a liquid through said thin pipe from said introduction port to said discharge port.
(3) The precision screw pump according to (2) wherein said cylindrical needle comprises a smooth-surface substance having a predetermined strength.
(4) The precision screw pump according to (2) or (3) wherein the filaments constituting said rotor are covered with the smooth-surface substance.
(5) The precision screw pump according to any one of (2) to (4) wherein said rotor has a screw angle set between 15 and 35xc2x0 relative to a rotational center axis.
In addition, the present invention provides a rotor for a screw pump as described below.
(6) A rotor for a screw pump manufactured by twisting up a plurality of filaments into a screw.
Further, the present invention includes the following method for producing a photocurable resin the above rotor for a screw pump.
(7) A method for producing the rotor for a screw pump rotor according to (6), the method comprising
providing a plurality of filaments,
coating an adhesive on the filaments,
twisting up the filaments, and
curing the adhesive to give a screw pump rotor.
(8) The method according to (7), wherein the adhesive is a photocurable resin.
In addition, a basic concept of the present invention is a biological liquid injection and ejection instrument as described below.
(9) A biological liquid injection and ejection instrument comprising a micro screw pump formed of a hollow needle.
(10) A biological liquid injection and ejection instrument wherein a micro screw pump is formed of a hollow needle so that the hollow needle has a small diameter.
(11) A method of making a diameter of a hollow needle small, the method comprising making a hollow needle in the form of a micro screw pump.
The xe2x80x9cneedle-shaped or needlexe2x80x9d constituting the present screw pump can be shaped like a hollow cylinder and may have a flat or sharp tip, as shown in FIGS. 2A and 2B, respectively.
The xe2x80x9cintroduction or discharge portxe2x80x9d of the needle is not necessarily limited to predetermined one end. In other words, for liquid suction, a tip portion of the needle which is contacted with the surface of a liquid to be sucked is the introduction port, whereas a cylinder side of the needle is the discharge port. On the contrary, for liquid injection, one end of the needle which is connected to the cylinder is the introduction port, while another end of the needle which is inserted into a living body is the discharge port.
The liquid to be transferred by the present screw pump can improve its own fluidity in the needle when the rotor is moved, and includes not only a solated liquid, which has low viscosity but also a gelled liquid, which has high viscosity.
The xe2x80x9cscrew pumpxe2x80x9d constituting the present invention is comprised of a casing and a rotor so as to transfer a liquid by rotating the rotor. The xe2x80x9crotorxe2x80x9d is any rotor having a structure such as a xe2x80x9cthreadxe2x80x9d or a xe2x80x9cscrew structure,xe2x80x9d which can rotate a shaft to transfer the liquid in a fixed direction.
The xe2x80x9cplurality of filamentsxe2x80x9d constituting the rotor according to the present invention may be such a material as natural, synthetic, and metallic fibers, which can provide very thin fibers and which can be twisted up. Any material can be used as these filaments as long as it meets the above requirement.
In addition, the xe2x80x9crotor obtained by twisting upxe2x80x9d the plurality of filaments can be obtained by twisting up a plurality of filaments, and the filaments may be twisted in the left lay (Z twist) direction similarly to the thread of a right-handed screw or in the right lay (S twist) direction.
If the filaments are formed from a plastic material, a required rotor can be obtained simply by twisting up the filaments. If, however, the twisted materials are untwisted upon the rotation of the rotor, then a strong screw rotor can be obtained by applying an adhesive to the filaments before twisting them up and then curing the adhesive while maintaining the twisted state.
The rotor thus obtained may be soft enough to be bent upon rotation as long as it is prevented from being broken upon rotation.
According to the present invention, the filaments are coated or impregnated with the adhesive before twisting, and then the coated filaments are twisted up and cured. The xe2x80x9cadhesivexe2x80x9d for use in the present invention may be any adhesive, for example, anaerobic, thermosetting, or optically curing, as long as it can prevent a screw shape obtained through twisting from returning to the original shape after curing. A photocurable resin is preferred since it can be coated thin on the surface of the filaments and can be simply cured.
The xe2x80x9cphotocurable resin,xe2x80x9d as used herein, refers to a resin containing an oligomer having one or more functional groups in the molecule which can react to light irradiation to form a crosslinking structure, a monomer having one or more similar functional groups in the molecule, or both of such a oligomer and monomer. The oligomer includes a radical-polymerized photocurable resin such as an unsaturated polyester-based resin, an acrylic-based resin, an en-thiol-based resin, or a cationic-polymerized photocurable resin such as an epoxy-based resin (of course, a mixture of a novolak resin with a sulfonate of a diazonaphthoquinone, which is a photosensitive agent, may be used). Of these resins, the acrylic-based resin, particularly, an ester acrylate, an urethane acrylate, or an epoxy acrylate is preferred as the oligomer contained in the photocurable resin according to the present invention. In addition, the above monomer includes monomers for radical polymerization such as acrylic esters and methacrylic esters and monomers for cationic polymerization such as epoxy-containing compounds. The monomer for radical polymerization is preferred due to its curing speed and physical properties exhibited after curing.
The xe2x80x9cscrew angle set between 15 and 35xc2x0 relative to a rotational center axisxe2x80x9d refers to an angle at which the screw is formed relative to the rotational center axis as shown in FIG. 3. This range of angles represents the screw angle at which the liquid transfer capability of the screw pump according to the present invention can be improved, and those values which slightly deviate from this range are also included within the technical scope of the present invention if they similarly improve liquid transfer capability.
The xe2x80x9csmooth-surface substance having a predetermined strengthxe2x80x9d should be strong enough to avoid deformation even if the needle is inserted into the living body, and have smoothness enough to lessen the interfacial friction between an inner wall of the needle and a liquid flowing through the needle. Such a substance includes, for example, metal, metal with a predetermined coating, or plastic, and the plastic is preferred in terms of moldability.
The xe2x80x9csmoothnessxe2x80x9d refers to being smooth, and a rough material surface such as a metallic machined surface or an electrically discharged surface is not preferred.